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Offshore Seismic Permanent Reservoir Monitoring (commonly known as PRM) is a seabed-based technology that is becoming part of the reservoir engineer's toolkit in practicing better management of oil and gas fields. In its most commonly practiced form, PRM involves conducting 3D seismic surveys at repeatable time periods, generally somewhere between six months and two years. The time interval between surveys may be variable, and depends on the specifics of the reservoir being monitored. It has been demonstrated to be a technical success because, as fluids are injected and/or produced from a field, the seismic data change in response to the changes in the reservoir. The field implementation of PRM has now become a major geoscience and engineering activity yielding tangible results. This paper is an attempt to present an overview, facts, and opinions that will be of use to engineers and geoscientists who are interested in what has been done, and what may be done, in the use of seismic permanent reservoir monitoring, or oilfield surveillance. The PRM market appears to be on an upswing, but it remains to be seen if that upswing continues. There are several reasons that have tempered the adoption of this technology. Two are being emphasized here. One is that it has been difficult to determine and publicize the cost-effectiveness of PRM. While upfront costs are relatively large compared to many geological and geophysical activities, they are not large when compared to overall field development, optimization, and maintenance costs. Companies are now taking a more realistic look at the ultimate value derived from PRM due to the growing number of published benefits versus cost. The second moderating reason emphasized here is the number of stakeholders, with a wide variety of technical expertise, perspectives, objectives, and motivations, which must be involved in approving and executing such a project. This situation is being addressed as more corporate leaders are made aware of how PRM may address, in addition to production and operational needs, a number of health, safety, and environmental (HSE) concerns, broadening the interested constituent base within operating companies, and further establishing the benefits, both technical and economic, of PRM. There are currently 13 installed PRM projects, with the longest-running (Valhall) having been operating since 2003. The high-quality seismic data obtained from these projects are capable of showing very small changes in seismic amplitude and/or travel time that result from changes in the reservoir and its contents, such as fluid type, saturation, and pressure. The seismic systems themselves have also become the vehicle to integrate other measurements at the seafloor, such as temperature, water chemistry, or small changes in seafloor topography – all parameters that may have HSE implications. The growing importance of this oilfield surveillance approach will ultimately result in a variety of engineers collaborating not only with geoscientists, but also with other departments within the corporation such as Quality and HSE. As shown by the technical and economic successes of at least two projects (Valhall and BC10), the appropriate use of a PRM system significantly increases recovery, production rates, and operational efficiency, and reduces reservoir management costs (Chen and others, 2015, Barkved, 2012, Caldwell, 2009, Caldwell and others, 2015). |
